This paper examines how the interplay of frequency and semantics may have influenced the directionality of the change of the compound tense auxiliary system in Spanish, taking the near-synonymous verbs <i>tornar</i> and <i>volver</i> (&#8216;to return&#8217;) in the 16th century as examples. There is a significant contrast in the auxiliary selection of the two verbs that can be explained by taking into account the differences in semantic usage of the two verbs, as well as frequency effects. On the one hand, the higher degree of motional usage of <i>volver</i> leads to the more frequent selection of <i>ser</i>. On the other hand, the higher usage frequency of <i>volver</i> led to a conservation of the usage of the <i>ser</i>-auxiliary with this verb. In consequence, the chapter argues for a joint influence of semantic usage and frequency effects on the development of auxiliary selection in Spanish.